text: Analytical thermal desorption originated in the mid-1970s as an adaptation to the injection procedure for GC. Injector liners were packed with a compound able to adsorb organic compounds, used to sample air or gas, and then dropped into the inlet of the GC. This principle was first widely employed for occupational monitoring, in the form of personal badge-type monitors containing a removable charcoal strip. These offered the advantage of being amenable to analysis without a separate solvent-extraction step.
  Also developed in the 1970s was a method by which volatiles in the air were collected by diffusion onto tubes packed with a sorbent, which was then heated to release the volatiles into the GC system. These were first introduced for monitoring sulfur dioxide and nitrogen dioxide, but the analyte scope later widened as the sorbents became more advanced. Another early method (closely related to the modern purge-and-trap procedure) involved passing a stream of gas through a water sample to release the volatiles, which were again collected on a sorbent-packed tube.
  Such axial-type samplers, which later became known as sorbent tubes, were laid out as an industry standard in the late 1970s, by Working Group 5 (WG5) of the UK Health & Safetys Committee on Analytical Requirements (HSE CAR). The tubes they outlined were  inches long with an outer diameter of  inch, and were first employed in Perkin Elmers ATD-50 instrument.
  At the same time, WG5 specified various basic functionality requirements for thermal desorption, and in the years since then, a number of improvements have been made to instrumentation for thermal desorption, including two-stage operation (see below), splitting and re-collection of samples, improved trap-cooling technology, standard system checks, and automation.